Microsurgical instruments typically are used by surgeons for removal of tissue from delicate and restricted spaces in the human body, particularly in surgery on the eye, and more particularly in procedures for removal of the vitreous body, blood, scar tissue, or the crystalline lens. Such instruments include a control console and a surgical handpiece with which the surgeon dissects and removes the tissue. With respect to posterior segment surgery, the handpiece may be a vitreous cutter probe, a laser probe, or an ultrasonic fragmenter for cutting or fragmenting the tissue and is connected to the control console by a long air-pressure (pneumatic) line and/or power cable, optical cable, or flexible tubes for supplying an infusion fluid to the surgical site and for withdrawing or aspirating fluid and cut/fragmented tissue from the site. The cutting, infusion, and aspiration functions of the handpiece are controlled by the remote control console that not only provides power for the surgical handpiece(s) (e.g., a reciprocating or rotating cutting blade or an ultrasonically vibrated needle), but also controls the flow of infusion fluid and provides a source of vacuum (relative to atmosphere) for the aspiration of fluid and cut/fragmented tissue. The functions of the console are controlled manually by the surgeon, usually by means of a foot-operated switch or proportional control.
During posterior segment surgery, the surgeon typically uses several handpieces or instruments during the procedure. This procedure requires that these instruments be inserted into, and removed out of the incision. This repeated removal and insertion can cause trauma to the eye at the incision site. To address this concern, hubbed cannulae were developed at least by the mid-1980s. These devices consist of a narrow tube with an attached hub. The tube is inserted into an incision in the eye up to the hub, which acts as a stop, preventing the tube from entering the eye completely. Surgical instruments can be inserted into the eye through the tube, and the tube protects the incision sidewall from repeated contact by the instruments. In addition, the surgeon can use the instrument, by manipulating the instrument when the instrument is inserted into the eye through the tube, to help position the eye during surgery.
Many surgical procedures require access to the sides or forward portion of the retina. In order to reach these areas, the surgical probes must be pre-bent or must be bendable intra-operatively. Various articulating optical surgical probes for providing laser and/or illumination light are known. See for example, U.S. Pat. No. 5,281,214 (Wilkins, et al.) and U.S. Pat. No. 6,984,130 (Scheller, et al.). The articulation mechanism, however, adds extra complexity and expense. One flexible laser probe needing no articulation mechanism is commercially available, but this device uses a relatively large diameter optical fiber sheathed in a flexible tube comprising the distal tip, resulting in a large bend radius and large distal tip diameter with significant bend stiffness. These characteristics require that the distal tip contain a non-bent straight portion for ease of insertion of the bent portion, which must flexibly straighten as it passes through the hubbed cannula. The straight portion of the distal tip allows the bent portion to flexibly pass through the hubbed cannula before the distal cannula of the handpiece enters the hubbed cannula, to allow maximum bending clearance of the flexible portion, thereby minimizing the bending strain and corresponding frictional insertion forces. Such a large bend radius, large diameter flexible tube, and straight distal tip causes the useable portion of the fiber to extend a relatively long distance from the distal tip of the probe and limits access of the probe.
A further disadvantage in the known art is the flexibility of the distal cannula, which is a function of the material properties and cross sectional moment of inertia, as determined by the gauge size of the outside diameter of the cannula to fit within the hubbed cannula, and the inside diameter of the cannula to accept the flexible tube. For any given material, the outer and inner diameters of the cannula determine the flexibility of the cannula. This flexibility limits the surgeon's ability to use the instrument to manipulate the position of the eye during surgery.
A flexible-tip probe is disclosed in U.S. Patent Application Publication 2009/0093800 (Auld, et al.) that does not require a straight portion of flexible tube, which thus provides a more compact useable tip length, thereby allowing greater access to internal posterior structures of the eye without compromising insertion forces. The flexible-tip probe provides increased rigidity of the distal cannula to facilitate manipulation of the position in the eye during surgery. While this probe provides a relatively smaller cross section as compared to the previous probes, such as those disclosed by Scheller et al., it does not provide controllable articulation over a range of angles in the manner those probes do.